The field of the disclosure relates generally to three-phase power conversion systems and, more particularly, to a modular embedded multi-level converter (MEMC) and a method of use thereof.
Most known multi-level converters have several advantages over ordinary two-level converters, e.g., improved power quality, relatively higher efficiency due to lower switching frequencies, and the ability to interface between a grid and one or more renewable sources, such as photovoltaics (PVs), fuel cells, and wind turbines.
At least some known multi-level converters are configured with a modular structure and without transformers. The modular structure facilitates stacking of such known multi-level converters scaling to various power and voltage levels. Examples of such a multi-level converters include a modular multi-level converter (MMC) and an MEMC. MMCs and MEMCs employ large numbers of fully controllable semiconductor switches, such as insulated gate bipolar transistors (IGBTs), metal oxide semiconductor field effect transistors (MOSFETs), field effect transistors (FETs), gate turn-off thyristors, insulated gate commutated thyristors (IGCTs), injection enhance gate transistors (IEGTs), silicon carbide based switches, gallium nitride based switches, and gallium arsenide based switches, arranged in stacks that variously couple branches to a direct current (DC) side of the multi-level converter.
Energy balancing is an important aspect of operating a multi-level converter. In an MEMC, energy is balanced at a system level, which facilitates equalizing power on the alternating current (AC) side and power on the direct current (DC) side. Energy is further balanced among branches of the MEMC and within the branches. Furthermore, branch energy balancing techniques employed in MMCs, which rely on current distributions among the phase branches coupled in parallel between DC busses, are inapplicable in MEMCs where phase branches are serially coupled between the DC busses.